Large Third-order Optical Nonlinearity Research Articles

Design and realization of plasmonic nanostructures with large third-order optical nonlinearity

We designed an optical structure comprising plasmonic and dielectric materials that exhibits large third-order optical susceptibility and low-power consumption. Finite-difference time-domain simulation results were used to select tightly-packed gold nanosphere (AuNS) film, indium tin oxide (ITO) films, and gold (Au) thin film to construct AuNS/ITO/Au sandwiched nanostructures. Local-field enhancement factors up to 425 and large third-order optical susceptibility (χ(3)) with an amplitude order of 4.4 × 10−2 esu were achieved under an excitation power of 0.1 mW. These χ(3) results are exceptionally high, thereby rendering AuNS/ITO/Au a promising material for future applications in optical switches and related nonlinear optical devices.

Cavity-enhanced large third-order optical nonlinearity in AuNRs/ITO/Au plasmonic nanostructures

A sandwich plasmonic nanostructure (AuNRs-ITO-Au) composed of random-distributed gold nanorods (AuNRs) film, an indium tin oxide (ITO) space layer, and gold thin film was prepared by using sputtering methods. Third-order optical nonlinearities were investigated by using the Z-scan technique under ultralow excitation laser powers. Fifteen times of third-order optical susceptibility (χ(3)) enhancement has been obtained in AuNRs/ITO/Au compared to pure AuNRs at 880 nm. The FDTD simulation demonstrates that this enhancement is due to the further confinement of the electric field inside the sandwich nanostructure. The results are significant and may find applications in ultralow-power all-optical switches and plasmonic waveguides.

Dispersion of the third-order optical nonlinearities in 2D (PEA)2PbI4 perovskite film.

We report the wavelength-dependent third-order optical nonlinearity of two-dimensional halide organic-inorganic perovskite (PEA)2PbI4 film experimentally. The high-quality two-dimensional (PEA)2PbI4 film prepared via confinement-assisted drop-casting process exhibits ultrafast optical response and large third-order optical nonlinearities, and the measured nonlinear refractive index is closer to the quantum perturbation model accounting for the excitonic effect. In addition, the wavelength-dependent optical response transition from self-focusing to self-defocusing, saturable absorption to reverse saturable absorption has been observed and investigated. The experimental results confirm the large third-order optical nonlinearities in (PEA)2PbI4 film and may make inroads toward developing cost-effective high-performance optoelectronic devices.

Large third-order optical nonlinearities of two-dimensional CsPbBr3 nanoplatelets

Metal halide perovskites show considerable optical nonlinearity and could be used for cost-effective nonlinear optical devices if their nonlinear susceptibilities can be improved. Here, we report large optical nonlinearity, including third-order nonlinear absorption, refraction, and two-photon absorption excited luminescence, of CsPbBr3 nanoplatelets with a thickness of two or three atomic layers and a plane size of about 60 nm. Specifically, the nonlinear absorption was mainly induced by two-photon absorption at low incident powers, and the nonlinear absorption cross section reached 2.15 × 107 GM. It is two orders of magnitude larger than that of CsPbBr3 nanocrystals, which makes them an ideal optical limiting material. Furthermore, the nanoplatelets exhibited large self-phase modulation-induced nonlinear refraction, and the figures of merit W and T satisfied W >1 and T <1, which allow for optical switching. The large optical nonlinearity of CsPbBr3 nanoplatelets provides a basis for multifunctional applications in nonlinear optical devices.

Structural and Nonlinear Optical Properties of Polymer Base CdS, Cus and, Ag2s Quantum Dots

Synthesis of CdS, CuS and, Ag2S in the presence of PVA, as polymer stabilizer, was conducted by chemical bath way. The morphological studies followed by XRD (x-ray diffraction) and AFM (atomic force microscopy) revealed monolithic and small size quantum dots (QDs). The average size of QDs was 3.1, 3.2, and 3.4 nm average size for CdS, Ag2S, and, CuS, respectively. Uv-Vis absorption spectra of samples showed rutin behavior of decreasing absorption amount except CuS that had a minimum around 550 nm. The bandgap of samples was measured using absorption data is 4.3, 5.1 and, 5.2 (eV) for CdS, Ag2S and, CuS bandgap respectively. Nonlinear optical properties including nonlinear refractive index and nonlinear absorption of synthesized QDs were measured by Z-scan technique under 632.8 nm wavelength He_Ne CW laser. As we see from the figure.1, PVA/ Ag2S nanoparticles displayed reverse saturable absorber (RSA) and self-defocusing while PVA/CdS and PVA/CdS displayed saturable absorber and self-focusing behavior under the same condition. Concerning other similar researches [1-2], this work covered more vast types of nanoparticles and obtained and compared the differences.Figure.1. a)PVA/Ag2S, b)PVA/CdS, and c)PVA/CuS close aperture and d)PVA/Ag2S, e)PVA/CdS, and f)PVA/CuS open aperture date fitted by the theoretical function[1] Krishnakumar V, Shanmugam G, Nagalakshmi R. Large third-order optical nonlinearity of Mg-doped PbS/PVA freestanding nanocomposite films. Journal of Physics D: Applied Physics. 2012;45(16):165102.[2] Neo M, Venkatram N, Li G, Chin W, Wei J. Size-dependent optical nonlinearities and scattering properties of PbS nanoparticles. The Journal of Physical Chemistry C. 2009;113(44):19055-60. Figure 1

Strong near-infrared and ultrafast femtosecond nonlinearities of a covalently-linked triply-fused porphyrin dimer-SWCNT nanohybrid

Functional materials displaying large ultrafast third-order optical nonlinearities across a wide spectral region and broad temporal domain are required for all-optical signal processing. Particularly desirable is nonlinear optical (NLO) activity at near-infrared (NIR) wavelengths with femtosecond pulses. Herein the first triply-fused porphyrin dimer (TFP)-functionalized single-walled carbon nanotube (SWCNT) nanohybrid was successfully constructed by covalently grafting TFPs onto SWCNT. The results of Z-scan techniques demonstrate that the newly obtained TFP-SWCNT nanohybrid was found with a strong NLO performance under both nanosecond and femtosecond irradiation. In the nanosecond regime, an enhancement in optical limiting (OL) of the TFP-SWCNT nanohybrid is seen at 532 nm when compared with the performance of porphyrin monomer-functionalized SWCNT nanohybrid Por-SWCNT. Under femtosecond irradiation, the TFP-SWCNT nanohybrid exhibits a particularly strong OL effect with a giant two-photon absorption (TPA) cross section value (ca. 15,500 GM) at 800 nm pulses that mainly stems from intense TPA of TFP, in sharp contrast to the Por-SWCNT nanohybrid which exhibits only saturable absorption under identical irradiation. These results demonstrate that the newly-developed TFP-SWCNT nanohybrid is a very promising OL candidate for practical applications across wide spectral and temporal domains, and that covalently functionalizing carbon-based materials with triply-fused chromophores may be a useful approach to engineering adaptable photonic devices with broad-ranging NLO activity.

Large third-order optical nonlinearity of non-stoichiometric chalcogenide glasses within Ge-In-S ternary system

Third-order optical nonlinearity (TONL) of chalcogenide glasses (ChGs) in Ge-In-S (GIS) ternary system is characterized at two near-infrared wavelengths of 0.8 μm and 1.064 μm. It is found that the GIS ChGs with non-stoichiometric compositions exhibit extremely large TONL properties, and its origin has been explained from both aspects of glass structure and wavelength-dispersion dependence of the TONL properties. Nevertheless, calculation of figure of merits indicates that the GIS ChGs are suitable for n2-based TONL optical devices at long wavelength, while suitable for β-based devices at short wavelength.

Polarization-Independent Large Third-Order Optical Nonlinearity in Centimeter-Sized Random-Distributed Gold Nanorod Arrays

Random-distributed gold nanorod arrays (R-GNRAs) deposited on glass substrates have been systematically investigated through Z-scan, second harmonic generation (SHG), and dichromatic pump–probe mea...

Non-linear Thermo-Optical Properties of MoS2 Nanoflakes by Means of the Z-Scan Technique

The nonlinear thermo-optical response of MoS2 nanoflakes was investigated using the Z-scan technique, employing TM00-mode with a CW-laser diode operating at a wavelength of 532 nm. The systems were found to exhibit a strong nonlinear response, dominated by nonlinear refraction. The effect of the thickness of the MoS2 layer, deposited on a glass substrate, on the nonlinear susceptibility was studied. Furthermore, in this study, the effects of modifying the thickness of the MoS2 nanoflakes on the nonlinear optical phenomena, such as self-focusing and self-defocusing was investigated for the first time. In all cases, the nonlinear absorption and refraction were determined. The corresponding third-order susceptibilities and second-order hyperpolarizability were calculated to be as large as 10-7 (esu) and 10-32 (esu), under laser excitation, respectively. Showing large third-order optical nonlinearity suggests the potential of the MoS2 nanoflakes in photonics applications.

Study on The Third-Order NLO Properties of Trace Metal Ions in Nitric Acid Solution by Closed-Aperture Z-scan Technique

Discovery of materials which exhibit large real third-order optical nonlinearities have recently become the topic of a broad scientific interest, due to its potential applications in many areas especially in the field of all-optical signal-processing. Here in this work, we report a preliminary investigation on the third-order nonlinear optical (NLO) response of different type of trace metal ions in nitric acid standard solution. A facile and rapid single beam z-scan technique incorporating 532nm diode pump solid state laser was employed to study the response of Lead (Pb), Cadmium (Cd), Mercury (Hg), Zinc (Zn), Aluminum (Al) ions towards NLO properties. Nonlinear refraction (NLR) response of the heavy metal samples were recorded from closed-aperture output and the maximum values of nonlinear refractive index, n 2 for all Pb, Cd, Hg, Zn, Al were recorded at 1.96355×10−9, 3.38228×10−9, 9.36907×10−9, 8.67559×10−10,3.28211×10−9 cm2W−1 respectively. Based on the experimental findings, the negative sign of the nonlinear refractive index values successfully indicates that the samples exhibit nonlinear self-defocusing effect, which is further expected to have potential applications in all-optical devices.

Au nanocages saturable absorber for 3-µm mid-infrared pulsed fiber laser with a wide wavelength tuning range.

Au nanocages (Au-NCs) have attracted wide attention as low-dimensional materials with broadband absorption, ultrafast optical response, large third-order optical nonlinearity coefficient, and high photothermal stability and thermal tolerance. By employing Au-NCs as saturable absorbers, we demonstrate a widely tunable passively Q-switched erbium-doped fluoride fiber laser at the wavelength of 2.8 µm. When operates at 2778.0 nm, this laser delivers stable Q-switched pulses with a maximum average power of 584.6 mW at a pulse repetition rate of 80.6 kHz. The minimum pulse duration attained was 1.16 µs corresponding with the single pulse energy of 7.25 µJ. Our results present onefold increase in pulse energy over previously published values achieved from Au nanoparticles based 3-µm passively Q-switched fiber lasers. By introducing a plane ruled grating, a tuning rage of 57.0 nm from 2753.0 to 2810.0 nm is achieved, while maintaining stable Q-switched operation. To our knowledge, this is the first time to demonstrate that Au-NCs can realize mid-infrared pulsed laser. Our research results show that Au-NCs are promising broadband nonlinear modulators for mid-infrared pulse generation.

Structural property of bismuth-doped tellurite glasses for nonlinear and Raman fiber applications

A series of 75TeO2–(20−x)ZnO–5Na2O–xBi2O3 (mol%) glasses with x = 0, 6, 8, and 10 (TZN–Bi) were fabricated via the special melt-quench technique and characterized as candidates for fiber laser glasses. Optical absorption studies revealed that increasing the Bi2O3 content increased the cutoff wavelength and Urbach energy (ΔE) and decreased the optical band gap energy (Eopt): these trends were attributed to the structural changes occurring in these glasses. In addition to optimizing the linear transmittance and absorption, Bi2O3 increased the nonlinear refractive indexes and the Raman gain coefficients. The TZN–Bi glasses exhibited large third-order optical nonlinearities with a maximum n2 of 2.85 × 10−15 cm2/W. The peak Raman gain coefficients (29 × 10−11 cm/W) were approximately 30 times that of SiO2. These results indicate that the Bi2O3-modified glasses are promising candidates in optical applications such as Q-switching elements and Raman gain amplifiers. © 2019 Elsevier B.V. All rights reserved.

Passively Q-switching fiber lasers using acetone solution as a saturable absorber

Organic materials are attracting attention for their potential applications due to their large third-order optical nonlinearities. A passive fiber Q-switching laser has been demonstrated based on an erbium/ytterbium codoped amplifier and an acetone solution saturable absorber (SA). When pump power was increased from 120 to 155 mW, the repetition rate increased from 5.68 to 16.67 kHz, while the pulse width decreased from 24.1 to 15 μs. These results indicate that acetone solution can be used as an effective SA for pulsed lasers.

Large third-order optical nonlinearity and ultrafast optical response in thin Au nanodisks

Nanostructures with remarkable optical nonlinearity and ultrafast light response have enabled numbers of applications in the fields varying from physics to biochemistry, and even quantum science. Maximally increasing the optical nonlinearity and simultaneously reducing the light response time of nanostructure is regarded as a great challenge for the optics from both fundamental and applied. In this paper, we report unprecedentedly huge third-order nonlinearity and ultrafast property in the nanosystem of Au nanodisks with ∼7 nm thickness. Their thin thickness brings about large electric field enhancements, leading to the third-order nonlinearity susceptibility (χ(3)) reaching the order of 10−18 m2/V2 (∼10−10 esu), which is 1-3 orders of magnitude larger than that of other shapes of Au nanostructures in the same solution environment, such as nanospheres, nanorods and triangle nanoprisms. Furthermore, optical Kerr measurements demonstrate their optical response time is as fast as ∼100 fs. Our findings demonstrate the thin Au nanodisk can be a suitable candidate for ultrafast nonlinear optical devices, such as the all-optical switches and all-optical signal processing devices.

Twistacene contained molecule for optical nonlinearity: Excited-state based negative refraction and optical limiting

Spindle-type molecules containing twisted acenes (PyBTA-1 &PyBTA-2) are designed, synthesized characterized. Picosecond Z-scan experiments under 532 nm show reverse saturable absorption and negative nonlinear refraction, indicating large third-order optical nonlinearity in PyBTA-1. The mechanism of the optical nonlinearity is investigated and the results show that the nonlinear absorption and refraction in PyBTA-1 originates from a charge transfer (CT) state. Furthermore, relatively long lifetime and absorptive cross section of the CT state are measured. Based on the excited state absorption in PyBTA-1, strong optical limiting with ∼0.3 J/cm2 thresholds are obtained when excited by picoseconds and nanoseconds pulses. The findings on nonlinear optics suggest PyBTA-1 a promising material of all optical modulation and laser protection, which enrich the potential applications of these spindle-type molecules. Comparing to the previously reported spindle-type molecules with analogous structures, the introduction of ICT in PyBTA-1 &PyBTA-2 dramatically decreases the two-photon absorption while enhances the nonlinear refraction. The results could be used to selectively tailor the optical nonlinearity in such kind of compounds.

Large third-order optical nonlinearity in PdO thin films

We report on a study of the absorption spectra and third-order nonlinear optical properties of crystalline PdO thin films, grown by oxidation of thin palladium films deposited on a substrate. The spectra reveal an absorption peak at [Formula: see text][Formula: see text]nm, which grows and narrows significantly as the temperature is lowered to [Formula: see text][Formula: see text]K. This behavior suggests an exciton nature of the peak. According to the position of the long wavelength absorption edge in the spectra, the bandgap of the material is [Formula: see text][Formula: see text]eV. Utilizing the techniques of degenerate four-wave mixing and Z-scan, using a pulsed laser radiation with a wavelength [Formula: see text][Formula: see text]nm and a pulse duration of [Formula: see text][Formula: see text]ns, we determined the real part of the third-order nonlinear susceptibility of Re[Formula: see text][Formula: see text]esu. Possible nature of this high refractive nonlinearity is discussed.

Theoretical study on the spectroscopic and third-order nonlinear optical properties of two-dimensional charge-transfer pyrazine derivatives

ABSTRACTIn this paper, density functional theory method was employed to study the electronic absorption spectrum and electronic static second hyperpolarisability of X-shaped pyrazine derivatives with two-dimensional charge-transfer structures. Computational results show that the push–pull electron abilities of the substituent groups and the length of the conjugated chains affect the electronic spectrum and static second hyperpolarisability of the pyrazine derivatives. As the push–pull electron abilities of the substituent groups or the length of the conjugated chains increases, the frontier molecular orbital energy gap decreases, resulting in increased second hyperpolarisability and redshift of the electronic absorption bands. The electronic absorption spectra of the pyrazine derivatives maintain good transparency in the blue light band. The electronic static second hyperpolarisability exhibits a linear relationship to the frontier molecular orbital energy gap. Particularly, increasing/decreasing the push–pull electron abilities of the substituent groups considerably affect the static second hyperpolarisability in long conjugated systems, which is important to the modulation of molecular organic nonlinear optical (NLO) properties. The studied pyrazine derivatives show large third-order NLO response and good transparency in the blue light band and are thus promising candidates as NLO materials for photonics applications.

Ultrafast nonlinear optical response in solution dispersions of black phosphorus

We report the spatial self-phase modulation (SSPM) effect for solution dispersions of black phosphorus (BP). The experimental results suggest that this concentration-dependent coherent light diffraction is due to the ultrafast and large third-order optical nonlinearity of BP. The third-order nonlinear susceptibility of BP has been simply obtained about 10−19 m2/V2 by analyzing the experimental results. The fast relaxation time during dynamic relaxation is obtained as 0.13 ps. Our experimental results imply novel potential application of BP in ultrafast nonlinear phase modulation devices based on their nonlinear optical response.

New quinacridone derivatives: Structure-function relationship exploration to enhance third-order nonlinear optical responses

Exploiting synergistic cooperation between multiple sources of optical nonlinearity, we report the design, synthesis, and the third-order nonlinear optical (NLO) properties of a series of quinacridone-based materials with condensed π-systems, and sterically regulated inter-aryl twist angles. By introducing dicyanoethylene groups not only successfully modified the structures and photoelectric properties of the chromophores but also led to the superior third-order NLO properties. The relationships between molecular structure and mechanisms of the enhanced nonlinear refractive index were illuminated by spectroscopic, electrochemical, and Z-scan measurements. Combined with quantum chemical calculations, the test data and theory calculations were verified. The maximum nonlinear absorptive coefficients (χ(3)) in these materials based on chromophore QA-B2 is 15.456 × 10−13 esu, which is more than 5 times higher than that of mono-modified QA. Our results clearly suggest that quinacridone-based materials have good photo-thermal stability and large third-order NLO properties, are very promising for integrated NLO devices.

Large third-order optical nonlinearity in vertically oriented mesoporous silica thin films embedded with Ag nanoparticles

Taking advantage of the channel confinement of mesoporous films to prevent the agglomeration of Ag nanoparticles to achieve large third-order optical nonlinearity in amorphous materials, Ag-loaded composite mesoporous silica film was prepared by the electrochemical deposition method on ITO substrate. Ag ions were firstly transported into the channels of mesoporous film by the diffusion and binding force of channels, which were reduced to nanoparticles by applying suitable voltage. The existence and uniform distribution of Ag nanoparticles ranging in 1–10 nm in the mesoporous silica thin films were exhibited by UV spectrophotometer, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements. The third-order optical nonlinearity induced by Ag nanoparticles was studied by the Z-scan technique. Due to the local field surface plasmon resonance, the maximum third-order nonlinear optical susceptibility of Ag-loaded composite mesoporous silica film is 1.53×10−10 esu, which is 1000 times larger than that of the Ag-contained chalcogenide glasses which showed large nonlinearity in amorphous materials.